Combustion of fuel, particularly carbonaceous materials such as fossil fuels and waste, results in hot flue gas streams that contain impurities, such as mercury (Hg), sulfur oxides (SOX), nitrogen oxides (NOX), and particulates, such as fly ash, which must be removed or reduced to a more acceptable level prior to release of the flue gas to the environment. In response to regulations in place in many jurisdictions, numerous processes and equipment systems have been developed to remove or reduce impurity levels and/or particulates in flue gas.
Typical methods of reducing flue gas particulates, Hg, NOX, and SOX impurities from steam generating boilers powered by fuel combustion is through the use of flue gas treatment equipment. Such equipment includes for example electrostatic precipitators (ESP), fabric filter bag houses, selective catalytic reduction (SCR) systems, wet flue gas desulfurization (WFGD) systems and/or dry flue gas desulfurization (DFGD) systems.
In some flue gas stream processing systems, removal of acidic components, such as SOX, is facilitated through the use of a DFGD system, wherein a reagent slurry or solution is dispersed in the flue gas stream to react with the SOX present therein. Current DFGD systems utilize spray dryer absorber (SDA) vessels equipped with an atomizer system that receives a reagent slurry, typically in combination with a dilution liquid, and disperses the reagent or combination within the vessel for contact with the flue gas. Upon contact with the flue gas, the reagent slurry reacts with the impurities in the flue gas to produce dry powder products and a flue gas stream of reduced impurity content.
U.S. Pat. No. 4,226,603 discloses an atomizing device arranged centrally in an atomizing chamber. A processing gas is supplied around the atomizing device through a conical guide duct communicating with a horizontal spiral duct through an annular mouth. Processing gas distribution is adjusted by deflection of the gas stream from the spiral duct into the conical guide duct by means of two separate sets of stationary guide vanes arranged relatively close to and overlaying each other in the mouth. A damper is arranged along the mouth to control the ratio of the portions of the gas stream conducted into each of the two vane sets.
U.S. Pat. No. 4,481,171 discloses a spray reactor for flue gas desulfurization equipped with an atomizing disc to spray an alkaline reagent into a flue gas. Concentric inner and outer annular passages around the atomizing disc convey the flue gas. The outer passage flow is controlled by a series of dampers adapted to maintain a relatively constant flow velocity in the inner passage in response to turndown of the reactor load.
U.S. Pat. No. 4,519,990 discloses an atomizer located in an upper portion of a chamber for introducing a finely dispersed spray of aqueous medium, and a gas injection means for receiving a major portion of a hot gas stream for introduction circumferentially about the atomizer. An essential feature of the apparatus is that a minor portion of the hot gas stream is introduced into the chamber in a direction counter to the direction of swirl of the major portion of the hot gas stream passing downwardly through the chamber from about the atomizer.
U.S. Pat. No. 4,560,543 discloses an absorption chamber in which a stream of waste gas is injected downwards from an upper part thereof with an aqueous liquid containing an absorbent atomized into the gas stream. The water content of the aqueous liquid is adjusted depending on the drying capacity of the downward gas stream so the drying of the atomized liquid produces a particulate material having a moisture content of at least 3 percent by weight, to at least 10 percent by weight. A second gas stream is introduced upwards from a bottom part of the absorption chamber at a rate sufficient for fluidizing the moist particulate material within the absorption chamber.
U.S. Pat. No. 4,571,311 discloses a process gas treatment chamber with a pair of concentric, inner and outer annular gas inlet ducts surrounding a liquid spray apparatus. Partition means divide a spiral supply duct into independent inner and outer sub-ducts which define separate inner and outer flow passages connected respectively to the inner and outer annular gas inlet ducts. Damper means are provided in the inlet to the outer sub-duct to selectively control the flow of process gas there through as a means of maintaining the velocity of the flow of process gas through the inner flow passage at a minimum acceptable velocity.
U.S. Pat. No. 4,619,404 discloses a gas distribution arrangement with a helical inlet duct through an annular orifical slit for processing gas introduction into a space between two coaxial guide walls. Guide vanes are provided in the orifical slit to impart a change of direction to the flow of processing gas. Each guide vane is a spatial body with differently extending, vertical limitation surfaces which between adjacent vanes delimit ducts whose sectional area as measured transversely of the flow direction of the processing gas through the individual duct is substantially of the same size over the extent of the duct. The vertical height of the guide vanes may decrease along their radial extent inwards in the orifical slit, and their vertical limitation surfaces may form an acute angle at the radially innermost ends of the guide vanes.
A problem not addressed by the above-identified prior art, is the problem of undesirable harmonic or non-harmonic atomizer vibration. As known, a rotating component of a machine experiences harmonic oscillation at a particular speed of rotation due to speed and mass. Rotating a machine component at a speed in the component's harmonic range causes undesirable component oscillations or vibrations which thereby reduces the useful life of the machine component. Reducing the useful life of the machine component increases capital and operational costs associated therewith. Such is true of rotary atomizers used in SDA flue gas desulfurization systems. Depending on the speed at which the rotary atomizer is rotated, undesirable atomizer oscillations or vibrations result, thereby reducing the useful life of the atomizer, and increasing capital and operational costs associated therewith. Accordingly, an atomizer operable with lessened or without undesirable harmonic vibrations is needed.